Welch plug



106m ET AL 3,486,656

WELCH PLUG Filed Nov'. 12. 1968 Dec. 30, 1969.

FIG.

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United States Patent O 3,486,656 WELCH PLUG Kenneth R. Foote, China Lake, and John W. Haldeman, Fair Oaks, Califi, assignors to the United States of America as represented by the Secretary of the Navy Filed Nov. 12, 1968, Ser. No. 775,083 Int. Cl. B65d 39/02, 43/04 US. Cl. 22047 6 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus is provided for sealing a passageway in such a manner that the sealing device may be removed by application of a predetermined pressure Within the passageway.

GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention pertains to a removable closure device for a passageway and more particularly to such a closure device which provides a hermetic seal and which may be removed by application of sufficient pressure within the passageway. Such plugs are sometimes referred to as welch plugs and have been used in a variety of applications, for example, to seal the unused ends of drilled oil passages and to provide release of pressure in water jackets of water cooled internal combustion engines should the water freeze in the engine head.

The welch plug according to the present invention is particularly designed to be used to seal a passage in a housing containing explosive material. Previous methods of sealing passageways were found to have numerous drawbacks when applied to the closing of such a housing. Exist ing friction type plugs did not provide a hermetic seal and the resistance to removal was unpredictable. The injection of molten lead or lead alloy under pressure over a disk in a housing containing explosives was hazardous and although controllable confinement was possible, a hermetic seal was difiicult to attain.

SUMMARY OF THE INVENTION By this invention, an improved welch plug is provided wherein a spherically formed disk is completely flattened in the passageway to cause the periphery to enter a groove provided in the passageway providing a hermetic seal with sufficient interference to assure the necessary confinement of the contents. The force necessary to blow the welch plug out of the passageway is termed the confinement. The confinement obtainable by this invention is greater than can be obtained from either of the methods described above and provides a seal with the ability to successfully withstand wide temperature variation without functional deterioration.

The welch plug according to the present invention was desired to confine a charge of explosive powder in a signal device to meet requirements imposed by the use of a less hazardous powder. The powder selected is less hazardous because it is more difiicult to ignite but also it requires greatly increased confinement for proper operation. The improved welch plug seal according to the present invention provides controllable confinement with hermetic sealing to prevent moisture from getting into the powder and to provide a predictable removal pressure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIG. 1 is a diametral cross sectional view of a signal 3,486,656 Patented Dec. 30, 1969 ICC device incorporating a plug according to the present invention;

FIG. 2 is a diametral cross sectional view of a plug disk before placement in the device; and

FIG. 3 is a diametral cross sectional View of a modified signal device.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION FIG. 1 depicts a diametral cross sectional view of a pyrotechnic device 10 incorporating a plug according to the present invention. The body 12 of the pyrotechnic device is generally cylindrical and is adapted to be fitted into the housing of an aircraft, a missile body or the like. The body 12 fits into an adapter 14 which is adapted to be permanently attached to the aircraft or missile and the adapter is counterbored to receive a cover 16. A cylindrical gasket 17 is provided for a seal between the adapter 14 and housing 12 in radial direction and the O-ring 18 provides a seal in the longitudinal direction.

The body 12 is further provided with a central cup or well 22 which normally contains an explosive material 24 confined in the cup 22 by a cover plate 23 and a rupturable diaphragm 31. The cup 22 forms with the walls of the body 12 an annular chamber 20 which normally is filled with a visual aid marker material. The annular chamber is closed by a pad 29 and a backing 27 held in place by the plug member 25 and further sealed by means of a plastic material 21.

The explosive 24 is detonated through firing ports 30, 31 and through safety port 28 in the firing device 26.

Ignition of the explosive material 24 may be caused by electrical activation of a primer 37 aligned with firing ports 30, 31 when the firing device 26 is oriented to place the safety firing port 28 in alignment therewith. As Wlll be seen to the right of FIG. 1, the body 12 has a narrow portion 36 which is threaded to receive a packing nut 38 and is counterbored to receive a primer 37 seated in the counterbore with a potting compound 39. The packing nut 38 is centrally bored to allow passage of the wire from the primer 37.

The arming device 26 is retained in a transverse bore in body 12 by means of a washer 33 and a retaining ring 32. The arming device 26 is moved from a safe position to the armed position shown by removing a safety pin (not shown) which holds arm 35 in a safe position against the action of spring 34 which spring tends to keep the device in the armed position.

As shown in FIG. 2, the plug or disk 25 is formed with a substantially spherical contour before placement in the body. The backing plate 27 is first placed in the central cavity of body 12 and then the disk 25 is placed on top of the backing plate and pressure is applied to completely flatten the disk 25 so that the periphery thereof enters the groove provided in body 12.

The configuration of body 12 can be varied to control the amount of material which must be removed by the plug 25 when it is forced out of its seat by explosive 24.

The body 12 is fastened to adaptor 14 by removable bolts (not shown) and a dead air space is provided between body 12 and cover 16. However, in some applications, the body may be connected in a missile without the use of an adaptor and may take the form of the body 12 as illustrated in FIG. 3. In this modification the body 12a and the plastic filling material 21a advantageously are formed to the contour of the missile surface.

The body 12a is shown without any opening corresponding to the opening 30 in body 12. In this embodiment, the passage 28 of the firing device 26 is loaded with a detonator which acts to break through the metal of body 12 at that point which is thinner than the surrounding parts, being on the order of about 0.040 inch thick.

What is claimed is:

1. The method of sealing a passageway comprising:-

forming a shoulder within said passageway;

forming a groove in said passageway outwardly of said shoulder;

placing a web of hardened material on said shoulder with the top surface of said material coplanar with the inner wall of said groove;

providing a metal sealing disk of spherical configuration having a peripheral dimension coextensive with said passageway opening;

placing said disk in said passageway on said material;

and

completely flattening said disk so that the periphery of said disk enters said groove.

2. In a pyrotechnic device wherein a cavity is designed to be opened by explosive force, the improvement comprising:

a peripheral shoulder inside said cavity;

a relatively hard backing plate on said shoulder;

a peripheral groove in said cavity with an inner surface coextensive with the top of said hardened plates; and

a metal plug disk su'rmounting said hardened plate and extending peripherally into said groove.

3. Ordnance impact indicating means comprising:

a cup shaped body having a scalable cavity;

explosive means located centrally of said cavity and forming with said body a torroidal chamber;

said cup shaped body including a base portion having a first bore concentric with said cavity and said explosive means, and a second bore normal to and intersecting said first bore;

rotatable shaft means in said second bore having therein a third bore which may selectively be positioned in alignment with or out of alignment with said first bore;

an explosive initiating means in said second bore opposite said explosive means; and

means in said torroidal chamber which will produce a signal when affected by detonation of said explosive means.

4. An indicating device according to claim 3 including adaptor means for fastening said device in a missile; and

said adaptor means including means for preserving the aerodynamic contour of the missile and means for protecting said device from aerodynamic heating.

5. The indicating device of claim 4 wherein said adaptor means includes:

producing means and said explosive means are hermetically scaled in said body;

said body including a portion adapted to be explosively ruptured; and said second bore containing a detonating means.

References Cited UNITED STATES PATENTS 8/1961 Williams 220-47 X 8/1968 Cottrell 22047 GEORGE T. HALL, Primary Examiner U.S. Cl. X.R. 

